Today urbanization has presented largely and thus communities and multi-storey buildings have become a good choice for living environment. However, men into and out of the communities and multi-storey buildings are numerous and hard to be monitored and controlled, and thus a security issue is arisen. Generally, guardian rooms are established and intercoms are provided so that men into and out of the communities and multi-storey building may be identified. For further guaranteed security, identification devices may be installed at doors and elevators of the communities and multi-storey building to avoid any non-inhabitant from invading.
However, this scheme may have shortcomings. When the habitant is not home or cannot answer the intercom, a visitor or others may not be identified in front of a guardian at the guardian room. To solve this problem, the habitant is requested to leave an emergency telephone number at the guardian room so that the visitor may be identified through telephone. However, privacy exposure may become another issue for the inhabitants.
To overcome this problem, a prior art “DOOR INTERCOM SYSTEM” also disclosed by the Inventor of the present invention is provided. In the door intercom system, a database is built in the door intercom system to store telephone number/cellular phone numbers of all the inhabitants in the same community. With the inhabitant's telephone number/cellular phone numbers in the database, the visitor may communicate with the inhabitant he/she intends to visit through a public switched telephone network (PSTN). Further, the inhabitant may remotely open or close his/her door through telephone. Although provision of the PSTN may solve the problem of inconvenience when the door intercom system is used, such communication manner through the PSTN is higher in cost. Further, the communication may not be visually obtained with an economic budget allowed by using the PSTN. As a result, the inhabitant may not identify if the visitor is exactly the one as communicated on telephone. In this manner, security may not be completely guaranteed for such door intercom system.
In view of these problems encountered in the prior art, the Inventor has paid many efforts in the related research and finally developed successfully a door intercom system in which a network and PSTN are utilized alternatively so as to promote convenience and security of such system.